As an example of an ADC, a successive approximation ADC converts a continuous analog waveform into a discrete digital representation via a binary search through all possible quantization levels before finally converging upon a digital output for each conversion. With increasing numbers of bits and a capability to operate at lower reference voltages, testing of ADCs is becoming challenging and expensive. For example, a 12 bit-ADC with a 3.3V voltage reference has a least significant bit (LSB) of
  LSB  =                    3.3        ⁢                                  ⁢        V                    2        12              =                  ~        800            ⁢                          ⁢              uV        .            Test instruments must have even better direct current (DC) accuracies.
There are numerous approaches for testing ADCs. One approach is to use mixed-signal automatic test equipment that can provide an accuracy of 1-2 mV. One approach is to set test limits beyond an ADC's specification which may mean that the ADC's specification is not fully verified in production testing. Accepting yield loss because of poor tester accuracy is also an option. This approach is disadvantageous because of insufficient test results that do not provide adequate reliability in operation of the ADC.